Marquis Williams and Taylor Poindexter at first thought they heard a balloon popping. When the loud bangs kept coming, the Chicago couple and fellow video gamers attending a weekend tournament recognized them as gunfire and began scrambling for an exit.

As he fled, Williams, 28, said, he could see the back of the gunman’s head as the attacker appeared to be walking backward as he fired.

“We didn’t see like a face,” Poindexter, 26, told reporters a few hours after the attack, standing on crutches after spraining her ankle trying to escape. “We did see him with two hands on a gun, walking back just popping rounds.”

The couple said people trampled others in the panic to escape. They ran to a nearby restaurant, where workers were waving people inside, and hid in a bathroom until police arrived.

The deadly violence stunned gamers competing Sunday in Jacksonville during a “Madden NFL 19” video game tournament. Jacksonville Sheriff Mike Williams said the gunman killed two people and shot nine others before fatally shooting himself.

The competition was held in a gaming bar that shares space with a pizzeria. Viewers could watch the games online and see the players.

Williams said authorities believe 24-year-old David Katz of Baltimore carried out the attack using at least one handgun at the Jacksonville Landing, a collection of restaurants and shops along the St. Johns River. He said final confirmation of the suspect’s identity was pending as the FBI in Baltimore aided in the investigation.

The sheriff said Katz was attending the tournament in Florida. The “Madden” game’s maker, EA Sports, lists a David Katz as a 2017 championship winner.

Authorities did not give a motive for the shootings.

“No one deserves to die over playing a videogame, you know?” said “Madden” competitor Derek Jones, 30, of Santa Fe, New Mexico. “We’re just out here trying to win some money for our families and stuff.”

Jones said he was sitting in a back patio outside the tournament venue when he heard the gunshots Sunday. He jumped a fence and ran, leaving behind his backpack and cellphone.

“You know, I’m glad I lost today,” Jones said. “Because if I’d won, I would have been in that game bar right then playing a game and not paying attention. And he could have come and I’d probably be dead right now.”

Jones said he knew Katz by the gamer tags he used online — often “Bread” or “Sliced Bread” — and had played against him online but had never spoken to him personally.

Nine other people wounded by the gunfire were all in stable condition Sunday evening after being taken to hospitals, Williams said. He added that two others were injured in the rush to flee the gunfire.

Investigators were looking into an online video that appeared to capture the scene right before the shooting began, Williams said. A red dot that appears to be a laser pointer is visible on the chest of a player seconds before the first of about a dozen gunshots rings out.

Jason Lake, the founder and CEO of compLexity, a company that owns professional esports teams, said on Twitter that one of his players, 19-year-old Drini Gjoka, was shot in the thumb.

On Sunday evening, the FBI said, its agents searched a family home of the man authorities believed was behind the attack.

Heavily armed agents, some in bulletproof vests and brandishing long guns, could be seen entering an upscale townhome complex near Baltimore’s Inner Harbor.

An FBI spokesman, Dave Fitz, confirmed that agents had gone to the house of the man’s father in Baltimore. He declined to release specifics, citing the ongoing investigation. T.J. Smith, chief spokesman for the Baltimore Police Department, also said that the agency was assisting law enforcement partners “with some information that has led authorities to Baltimore.”

In Washington, White House spokeswoman Sarah Huckabee Sanders said President Donald Trump had been briefed on the attack and the White House was monitoring the situation.

The Jacksonville Landing, in the heart of the city’s downtown, also hosts concerts and other entertainment. It was the site of a Trump rally in 2015, early in his campaign for the White House.

Marquis Williams said the shooting rampage was another tragic sign that elected officials should take action to curb gun violence.

“Politicians, wake up because the people you’re supposed to be representing are dying,” Williams said. “Quit sitting on your butts. Quit collecting checks and do something.”

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Farrington reported from Tallahassee, Florida. Associated Press Writer Tamara Lush contributed to this report from the Tampa area and Laura Heald from Jacksonville, Florida.